Electric potential shaping method for electroplating

Abstract

An apparatus for depositing an electrically conductive layer on the surface of a wafer comprises a flange. The flange has a cylindrical wall and an annulus attached to a first end of the cylindrical wall. The annulus shields the edge region of the wafer surface during electroplating reducing the thickness of the deposited electrically conductive layer on the edge region. Further, the cylindrical wall of the flange can be provided with a plurality of apertures adjacent the wafer allowing gas bubbles entrapped on the wafer surface to readily escape.

We claim: 
     
       1. A method of treating a surface of a substrate comprising: providing a cup attached to a flange, said cup having an inner perimeter which defines a cup central aperture, said flange comprising an annulus;   mounting said substrate in said cup so that said substrate surface is exposed through said cup central aperture;   placing said cup and flange into a plating solution, said plating solution contacting said substrate surface;   producing an electric current between said substrate surface and an anode in said plating solution, said electric current being represented by electric current flux lines, the spacing between the flux lines being proportional to the magnitude of the electric current; and   positioning said flange to reduce the spacing of the electric current flux lines adjacent an inner perimeter of said annulus while allowing said flux lines to spread out adjacent an edge region of said substrate surface such that said flux lines are substantially uniformly spaced across said substrate surface.   
     
     
       2. The method of claim 1 wherein producing an electric current comprises producing a voltage differential between said substrate surface and said anode. 
     
     
       3. The method of claim 1 wherein said annulus comprises a dielectric material. 
     
     
       4. The method of claim 3 comprising causing an electrically conductive layer to be deposited on said substrate surface and positioning said annulus to reduce the thickness of said electrically conductive layer on said edge region of said substrate surface. 
     
     
       5. The method of claim 1 comprising introducing ions of an electrically conductive material into said plating solution. 
     
     
       6. The method of claim 1 wherein said annulus causes said flux lines to be reduced adjacent said inner perimeter of said annulus as compared with a central region of said plating solution located radially inward from said inner perimeter. 
     
     
       7. The method of claim 1 comprising causing a portion of said electric current to flow between said anode and said substrate surface via a path which extends outside said annulus and through an aperture between said annulus and said substrate. 
     
     
       8. A method of treating a surface of a substrate comprising: providing a cup attached to a flange, said cup having an inner perimeter which defines a cup central aperture, said flange comprising an annulus;   mounting said substrate in said cup so that said substrate surface is exposed through said cup central aperture;   placing said cup and flange into a plating solution, said plating solution contacting said substrate surface;   directing said plating solution towards the center of said substrate surface; and   producing an electric current between said substrate surface and an anode in said plating solution wherein said annulus of said flange shapes flux lines of said electric current.   
     
     
       9. The method of claim 8 wherein said flange comprises a cylindrical wall having one or more apertures therethrough, said method further comprising directing said plating solution to flow radially outward from said center of said substrate surface and through said one or more apertures. 
     
     
       10. The method of claim 9 wherein directing said plating solution comprises removing gas bubbles entrapped on said substrate surface through said one or more apertures. 
     
     
       11. A method of treating a surface of a substrate comprising: providing a cup attached to a flange, said cup having an inner perimeter which defines a cup central aperture, said flange comprising an annulus;   mounting said substrate in said cup so that said substrate surface is exposed through said cup central aperture;   placing said cup and flange into a plating solution, said plating solution contacting said substrate surface;   rotating said cup, flange and substrate; and   producing an electric current between said substrate surface and an anode in said plating solution wherein said annulus of said flange shapes flux lines of said electric current.   
     
     
       12. A method of treating a surface of a substrate comprising: providing a cup attached to a flange, said cup having an inner perimeter which defines a cup central aperture, said flange comprising an annulus;   mounting said substrate in said cup so that said substrate surface is exposed through said cup central aperture;   placing said cup and flange into a plating solution, said plating solution contacting said substrate surface;   introducing copper ions into said plating solution; and   producing an electric current between said substrate surface and an anode in said plating solution wherein said annulus of said flange shapes flux lines of said electric current.